Above is our "line of defence" in our body.
The structure of skin can be divided into 5 categories:
1- Epidermis, dermis, subcutaneous layer
2- Sweat glands
3- Oil glands (sebaceous glands)
4- Hair and nails
5- Melanin
Epidermis
- This is the outer layer of our skin (what we see), and it is made up of stratified squamous epithelial tissue.
- Our skin cells are constantly flaking off, so new epidermal cells are produced in the deepest sublayer of the epidermis, and then pushed towards the outer surface as they mature.
- The epidermis cells contain a structural matrix of Keratin. This is a protein which is essentially waterproof, and which aids in the flexibility and elasticity of the skin.
- The epidermis is NON VASCULAR. This means that there are no blood vessels.
- The epidermis contains melanin, which provides the pigment in our skin
Dermis
- This is a thick layer below the epidermis.
- Consists of connective tissue which is made up of collagen fibres. Collagen is responsible for the strength and stretching of the skin.
- The dermis is VASCULAR. This means that are are blood vessels and nervous found throughout the layer.
- The upper portion of the dermis has "dermal papillae" that project into epidermal tissue. These papillae delivery oxygen and nutrients to the cells of the epidermis and help with temperature regulation.
Subcutaneous layer
- This layer is also known as the "superficial fascia."
- It contains loose connective tissue, as well as lots of fat (adipose) tissue.
- The function of this layer is to attach the skin to the muscles and tissues beneath.
- It also helps protect the underlying organs from mechanical shock.
- Distribution of fat in this layer is responsible for male and female body shapes.
Sweat glands
- Sweat glands are tiny coiled tubes in the dermis or subcutaneous tissue. They have a duct which extends up through the skin and opens onto the surface.
- There are over 3 million in skin
- Their functions include regulating temperature and eliminating waste.
- We sweat approximately 1 quart/day
Sebaceous glands
- These are also known as oil glands.
- They are generally attached to hair follicles, so are mostly present on the face and the scalp.
- They secrete sebum (an oily substance) which helps lubricate the surface and prevent water loss.
- They have an anti fungal property, as well as inhibit the growth of bacteria.
- An accumulation of sebaceous glands cause blackheads.
- They are relatively inactive in childhood, but are active during and after puberty.
Hair
- Hair is found everywhere on our body except for our palms and soles.
- It has a protective function.
- The part of the hair that we see is called the shaft, the root lies below the surface.
- At the bottom of the hair follicle, a bundle of connective tissue can be found which delivers nutrients to the follicle.
- Hair is formed from Keratin.
Nails
- Nails are mainly for protection.
- They are developed from epidermal cells, and contain compressed keratin.
- Nails appear pink due to underlying capillaries
Melanin
- Melanin is responsible for pigment in our skin.
- These cells are scattered throughout the lowest layer of the epidermis.
- Albino's cannot produce melanin, and therefore are extremely pale.
- When melanin cannot absorb all of the ultraviolet rays due to sun exposure, we get a sunburn.
Random facts about skin
- Total skin on our body is approximately 20 sq feet.
- Skin helps maintain homeostasis (internal balance).
- Skin helps protect us. It is part of the first line of defence.
- In order to determine how much water we have in our body, we must multiply our body weight (kg) by 0.6.
- For example: If we weight 60kg, we will have 36 L of water in our body. Out of this 36L, intercellular fluid accounts for 24L, while extracellular fluid accounts for 12L. If we further break down the extracellular fluid, 9L will be for interstitial fluid, and 3L will be comprised of plasma.
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